The present invention relates to a magnetic bubble memory. It applies to the storage of binary information in the form of isolated magnetic domains, called bubbles. These domains have a reverse magnetization to that of the remainder of the magnetic material constituting the layer in which they are formed.
It is known that each bubble can be displaced by a force and that this displacement can take place freely in a random direction in the plane of the magnetic layer. The latter is a magnetic garnet and the bubbles are formed in this garnet by applying a continuous magnetic field thereto, which is perpendicular to the plane of the layer. This field is produced by a permanent magnet, ensuring the nonvolatility of the information contained in the memory.
The magnetic garnet layer in which the bubbles are formed is generally supported by an amagnetic monocrystalline garnet.
It is also known to produce a bubble memory in an organization comprising a series of longitudinally oriented minor shift registers, and at least one transversely oriented major access register. These minor and major registers are constituted by patterns, whose boundaries are defined by the contours of ionically implanted zones of the magnetic garnet layer. In per se known manner, access register has one or more access points at one access end of each minor register. It is also known to use means for displacing the bubbles in each minor register by applying a rotating magnetic field and to use means for displacing the bubbles in the major register by circulating currents in two electrically conductive perforated sheets which are superimposed on the magnetic garnet layer, which are isolated from one another and from said layer and positioned facing the major register patterns. This known type of memory is, for example, described in French Pat. No. 2 480 983, whereof the application was filed on Apr. 18th 1980 in the name of the present Applicant.
In this known bubble memory, each bubble having to be transferred from a minor register to a major register must be disengaged from the boundary of the final pattern of the corresponding minor register in order to be propagated in to the major register, by means of electrical currents circulating in two sheets superimposed on the magnetic garnet layer. These bubbles circulate either in an implanted zone, or in an unimplanted zone and their guidance in the major register towards the access station requires the circulation of high currents in the conductive sheets, due to the fact that these bubbles, in the major register, are not permanently guided along the boundaries of the juxtaposed patterns.
The propagation of the bubbles by current circulation in electrically conductive sheets is also described in French Pat. 2 428 890. As in the memory described hereinbefore, as the bubbles no longer bear on the boundary of the patterns defined by ionic implantation, it is necessary to have a high current in order to guide the bubbles towards a given point.